Rheostat



June 15 1926.

W. W. WOOD RHEOSTAT Filed Sept. 1, 1922 Patented June 15, 1926.

PArs r oFi-"ics.

WALTER WOOD, OI canom omo.

muons-r.

Application med September 1, 1988. Is. 595,701.

The invention relates to means for varying the resistance of an electric current to control the amount of current flowing through the same; and the object of the .improvement is to provide simple means forcontrolling the strength of the current with a greater degree of refinement of adjustment, and for arriving at the critical value of the resistance more conveniently and quickly than has ordinarily been done.

In radio apparatus it is desirable, if not necessary, to adjust the electric current flowing through the filament of the detector or amplifying tubes to an exact critical value for the most efiicient operation of the same; and the present invention attains this result by means of an annular resistance coil mountedvon a relatively fixed support, an annular vernier wire mounted on a rotatf able disk and intermediate connected brushes mounted on an independently rotatable block, so arranged that an approximate adjustment me be obtained by rotating the brushes an the vernier wire together in one direction, and an exact adjustment may be obtained by rotating the vernier wire alone in the opposite direction.

The invention is illustrated in the accompanylilng drawings forming part hereof, in w c Figure 1 is a perspective view of the im proved rheostat;

Fig. 2, a perspective view of the parts thereof, in axial alignment for assembling; Fig. 8, an inner'end view of the rheostat; .Fi 4, an axial section of the same, on

i 9 F iht q f g. 5, a perspective view 0 the bruliea; Y v

Similar numerals refer to similar parts throughout the drawi comprise a square plate 6, with spacing- A supporting frame f: the rheostat may posts 7 extending inward from two opposite corners of the plate, and a. cross bar 8 extending across the ends of the posts; and

these parts maybe secured together by curto the panel 10 of a radio receiving box,

22. One end 26 of by bolts 11, at the alternate corners of the p ate. 1

A tubular bearing 12 is journaled in an axial bearing 13 provided in the supporting plate and panel. Upon the outer end of the tubular bearing may be secured a spacer block 14, carrying an indicating finger 15, as by means of a set screw 16; an upon the inner end of the tubular hearing is secured a radial brush block 17, as by means of a clamping screw 18.

An operating stem 19 is journaled in the tubular bearin Upon the outer end of the stem is secure an operating handle or button 20, as by means'of a set screw 21; and upon the inner end of the stem is secured a vernier disk 22, as by means of a current conducting pin 23 extending through the stem and the body of the disk to the periphery thereof. I o

An annular resistance coil Mis located in an annular groove 25 on the. inner side of the supporting plate. One end 24' of the coil terminates adjacent to and is connected by an extension wire with one of the conductin bolts 9; and the other end 24" of the co' terminates at a spaced interval from the circuit connected end, and has an insulated connection with the supporting plate.

A. vernier wire groove 27 around the tperiphery of the disk e vernier wire 26 is connected to the periphery end of the conducting pin 23, and the other end 26' of the wire terminates. at a subdantial interval from the circuit connected end, and has an insulated connection with the disk.

Brushes 28 and 29 are preferably made of resilient sheet metal strips in the form of to es cut from an integral sheet 30 folded to orm a spring plate 31on one side, and the brush sheet ma be secured tothe side of the brush block 1 asby rivets 32 extending through apertures 32' in the folded sheet.

One brush to e 28 extendsoutward beyond the end 0 the brush block, and is curved for slidi and yielding contact with the resistance coi The other brush tongue 29 extends inward over the end of the brush block, and is curved for a sliding and yield- 26 is located in a shallow ing contact with the vernier wire- The spring plate 31 extends outward from the brush block, and is curved for sliding and pressing frictional contact with the inner face of the supporting plate.

A spring conductor strip 33 is secured to the inner side of the connecting bar 8, as by means of a screw 34. One.end 33 of the spring strip is connected with the other circuit conducting bolt 9', and the other end 33" of the spring strip is in yielding pressing contact with the end of the operating stem 19; which end of the stem serves as a conductor to complete.the circuit between the conductor pin- 23 and the conductor strip 33.

The tubular bearing'lQ is held in position endwise on the operating stem 19, by the abutment of its outer end against the inner side ofs the operating button 20, and by the abutment of an annular shoulder 12 on the bearin against the outer side of the panel 10, T e operating stem is held in. posltion endwise by the abutment of the operating button 20 against the outer end of the tubular bearing 12, and the abutment of the disk 22 against the washer 35 located between the disk and the inner end of the tubular bearing. The inner face of the disk 22 is normallyspaced outward freely from the cross bar by action of the spring conductor strip 33, but the disk serves as a positive stop if the stem is pushed inward to overcome the pressure of the spring conductor strip upon its outer end.

A push pin 36 is provided on the outer side of the vernier disk adjacent to the circuit connected end of the vernier wire in thepath of the brush block, and in such a position that a rotation of the disk by a turning of the button will cause the push pin to iminge one side or the other of the brush hlock, so as to rotate it with the disk.

A stop pin 37 is provided on the inner face of the supporting plate 11 adjacent to the circuit connected end of the resistance coil in the pathof the brush block, and in I proper position to stop the brush block with the coil brush 28 in contact with thecircuit connected end of the coil, as indicated by broken lines in Fig. 1, when it is rotated by turning the top of the operating button and vernier disk to the right, as indicated by an arrowin Figs. 1 and 3 of thedrawings; in which position of the parts the vernier brush is in contact with the circuit connected end of the vernier wire and resistance of the coil and the wire is reduced to the minimum.

The same pin serves to stop the brush blockwhen'it is reversely rotated by a turning. of the button and disk to the left, after the brush 28 has passed beyond the end of the coil 24lof the resistance coil andstands freeof"thel coil, as shown in full lines, in Fig. earth's drawings; the same being the esaoaa 7 nected with the .conductor bolts 9 and 9';

and. when it is desired to close the circuit and adjust its strength by the rheostat, the same being in normal inoperative position, as shown in Fig. 1, the operating button is turned to the right, as indicated by the arrow, which rotates thevernier disk in the same direction, during which turning of the disk the friction action of the spring plate retards the brush block from turning and the vernier wire slides under the vernier brush 29, so that the brush is in contact with the circuit connected end 26' of the wire when the brush pin impinges the left side of the brush block.

A,further turning of the vernier disk to the right rotates the brush block in the same direction until the coil brush 28 contacts with the insulated end 24" of the resistance coil, as shown by-full lines, in

Fig. 3, whereupon the circuit is closed through the whole length of the resistance coil, but without including any considerable portion of the vernier wire.

A further turning of the disk to the right rotates the coil brush 28 in the same direction and gradually cuts out from the circuit a corresponding portion of the resistance coil 24 until the strength of the circuit is increased to a degree slightly beyond the desired critical value, as may be indicated by the filament or other means in the cir- When it is desired to reopen the circuit,-

the operating button. is rotated to the left until the push pin 36 on the vernier disk impinges the right side of the brush block, whereupon the brush block is rotated to the left until it impinges the stop pin 37 and the parts are brought into the normal position shown in Fig. 1.

The spacer block 14 rotates in unison with the brush block, and the indicating finger 15 thereon is properly positioned thereon to show to the operator the location of the brushes, if for any reason the same is necessary or desirable; but it is evident that the operation of the rheostat is automatically accomplished from normal osition, by mereturning the button to t e right to close 1 the circuit and to effect an approximate adrotating the disk alone.

- and 0011 re lane 2. A rheostat includi a support with an annular resistance coil t ereon, a rotatable disk with an annular resistance wire thereon, a rotatable block with connected brushes thereon for sliding contact with the wire and coil respectively, and means ior rotating the disk .and' block either way together, and for rotating the disk either way alone.

3. A rheostat including a support with an annular resistance coil thereon, a rotatable disk with anannular resistance wire thereon, a rotatable block with connected brushes thereon for sliding contact with thewire and coil respectively, and means for rotating either brush upon the corresponding resistance element and holding the other brush stationary upon the other resistance element. 4. A rheostat includin a support with an annular resistance coil 't ereon, a rotatable disk with an annular resistance wire thereon, a rotatable block with connected brushes thereon forslidin contact with the wire and means retarding rotation of t e bloc for sliding the resistance wire under the corresponding brush while the other brush is stationary on the resistance coil. Y

5. A rheostat including a support with an annular resistance coil th'ereon, av rotatable disk with an annular resistance wire thereon, a rotatable block with connected brushes thereon for sliding contact with the wire and coil respectively, and means on the disk for pushing the block either way I I for stopping with the disk, and means on the support rotation of the block one way with the c011 brush on the circuit connected end of the coil and the other way with the brush free of-both ends of the coil.

. 6. A rheostat including a support with an annular resistance coil thereon, a tubular bearing journal'ed in the support with connected brushes thereon, and an operating stem journaled in the tubular bearing with an annular resistance wire thereon, the brushes being arranged for sliding contact with the coil and the wire respectively.

7. A rheostat including a support with an annular resistance coil thereon, a tubular bearing journaled in the support with con-' nected brushes thereon, an operating stem journaled in the tubular bearing with an annular resistance 'wire thereon, the brushes being arranged for sliding contact with the coil and the wire respectively, and means on the tubular bearing indicating the position of the brushes thereon.

8. A rheostat including a relatively stationary support with a resistance element thereon, a'relatively movable support with another resistance element thereon, a movable block with connected brushes thereon for sliding contact along the respective re 's'istance elements, the movable support being mounted for movement either with or without the movable block.

9. A rheostat including a'relatively stationary resistance element and a relatively movable resistance element arranged to be connected in series, and connected brushes movably mountedfor sliding contact along the respective resistance elements, the movable resistance element being movable either Evithfior with respect to, the corresponding rus 1 10. A rheostat comprising, in combina-' member, a contact member loosely mounted relativel to said resistance members and having ictional engagement with each and means to move said secondary resistance member relatively to said contact member and the latter relatively to said primary resistance member to vary the resistance to an electric current passing therethrou h.

12. A rheostat comprising, in com ination, a rimary resistance member mounted in -fixe position, a secondary resistance member, a contact member loosely mounted relatively to said resistance members and having frictional engagement with each and means to move said secondary resistance member relatively to said contact member and said secondary resistance member and contact member in unison relatively to said primary resistance member to vary the resistance to an electric current passing therethrough. g

13. A rheostat comprising, in combination, a rimaryiresistance member mounted ondary resistance member and means to move in fixe position, a secondary resistance said secondary resistance member independmember, a contact member loosely mounted ently of said contact member and also in 10 relatively to said resistance members and unison therewith relatively to said primary having frictional engagement with each, said resistance member to vary the resistance to friction being greater relatively to said prian electric current passing therethrough. mary resistance member than to said sec- WALTER W. WOOD. 

